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Abstract:

The invention relates to a device and a method for determining and
indicating, on board of an airplane climate-relevant effects of a
contrail produced by the airplane. The method for determining and
indicating, on board of an airplane climate-relevant effects of a
contrail produced by the airplane includes determining radiation data of
short-wave and long-wave atmospheric radiation directed upwards in the
earth atmosphere at location of the airplane, determining air temperature
and air humidity at the location of the airplane, determining zenith
angle of the sun at the location of the airplane, determining a radiative
forcing value produced by the contrail based on the determined radiation
data, air temperature and air humidity, and the zenith angle, and
indicating at least one of the radiative forcing value and variables
derived therefrom.

Claims:

1. A device for determining and indicating, on board an airplane (101),
climate-relevant effects of a contrail produced by the airplane, the
device comprising: first sensor means for determining radiation data of
short-wave and long-wave atmospheric radiation directed upwards in the
earth atmosphere at a location of the airplane; second sensor means for
determining air temperature and air humidity at the location of the
airplane; a position means for determining zenith angle of the sun at the
location of the airplane; an evaluation means for determining a radiative
forcing value produced by the contrail based on the determined radiation
data, the air temperature and air humidity, and the zenith angle of the
sun; and an indication means for indicating at least one of the radiative
forcing value and variables derived therefrom.

2. The device according to claim 1, wherein the device further comprises:
a first interface to provide prognostic weather simulation data relating
to environment of the airplane to the evaluation means, wherein the
evaluation means comprises a first module that, based on the prognostic
weather simulation data, the radiation data, the air temperature and air
humidity, and the zenith angle, determines at least one of a lifespan of
the contrail and entire radiation effect of the contrail integrated over
its lifespan, and wherein the evaluation means determines the radiative
forcing value based on the integrated overall radiation effect of the
contrail.

3. The device according to claim 1, wherein the device further comprises:
a second interface to provide fuel consumption data of the airplane to
the evaluation means, wherein the evaluation means comprises a second
module that, based on the fuel consumption data, determines a radiation
effect of greenhouse gases emitted by the airplane, and wherein the
evaluation means determines the radiative forcing value additionally
taking into account the radiation effect of the emitted greenhouse gases.

4. The device according to claim 2, wherein the device further comprises:
a receiving unit for wirelessly receiving weather simulation data and for
providing the weather simulation data at the first interface.

5. The device according to claim 2, wherein the device further comprises:
a computer unit for generating and providing the prognostic weather
simulation data at the first interface.

6. The device according to claim 1, wherein the device further comprises:
a storage unit for storing at least one of the determined radiative
forcing value and the variables derived therefrom.

7. The device according to claim 1, wherein the device further comprises:
a transmitting unit for wirelessly transmitting the at least one of the
determined radiative forcing values and the variables derived therefrom
to a receiving station.

8. A method of determining and indicating, on board an airplane,
climate-relevant effects of a contrail produced by the airplane, the
method comprising: determining radiation data of short-wave and long-wave
atmospheric radiation directed upwards in the earth atmosphere at
location of the airplane; determining air temperature and air humidity at
the location of the airplane; determining zenith angle of the sun at the
location of the airplane; determining a radiative forcing value produced
by the contrail based on the determined radiation data, air temperature,
and air humidity, and the zenith angle; and indicating at least one of
the radiative forcing value and variables derived therefrom.

9. The method according to claim 8, wherein the method further comprises:
determining based on inclusion of provided prognostic weather simulation
data relating to the atmospheric environment of the airplane at least one
of a lifespan of the contrail and overall radiation effect of the
contrail integrated over the lifespan; and determining the radiative
forcing value based on the integrated overall radiation effect of the
contrail.

10. The method according to claim 8, wherein the method further
comprises: determining based on inclusion of fuel consumption data of the
airplane a radiation effect of greenhouse gases emitted by the airplane;
and determining the radiative forcing value based on the radiation effect
of the emitted greenhouse gases.

11. The method according to claim 9, wherein the method further
comprises: wirelessly receiving weather simulation data from a ground
station at the airplane; and making the weather simulation data available
on board the airplane for determining and indicating climate-relevant
effects of the contrail produced by the airplane.

12. The method according to claim 9, wherein the method further
comprises: generating weather simulation data on board the airplane; and
making the weather simulation data available on board the airplane for
determining and indicating climate-relevant effects of the contrail
produced by the airplane.

13. The method according to claim 8, wherein the method further
comprises: storing at least one of the determined radiative forcing
values and variables derived therefrom on board the airplane.

14. The method according to claim 8, wherein the method further
comprises: wirelessly transmitting the at least one of the determined
radiative forcing values and variables derived therefrom to a ground
station.

Description:

[0001] The invention relates to a device and to a method for determining
and indicating, on board an airplane, climate-relevant effects of a
contrail. The invention relates, in particular, to the field of civil
aviation.

[0002] It is known (compare J. E. Penner et al.: "Aviation and the Global
Atmosphere" IPCC, 1999, Technical Report, Cambridge University Press)
that climate-relevant effects of air traffic are due, in particular, to
the following three engine emission products: [0003] water vapour (1.25
kg), [0004] carbon dioxide (3.15 kg), and [0005] nitrogen oxides (5-25
g).

[0006] The above details in brackets are approximate details that state
the mass of the individual combustion products with combustion of 1 kg of
kerosene in modern engines in cruise flight. The climate-relevant effects
of the engine emission products are as follows. Carbon dioxide (CO2)
and water vapour (H2O) directly act as greenhouse gases. The
reactive nitrogen oxides NO, NO2, (NOx), which themselves are
not greenhouse gases, influence the formation of ozone (O3), which
in turn acts as a greenhouse gas. At a corresponding ambient air
temperature and humidity, the emission of water vapour (H2O) from
airplane engines furthermore causes the formation of condensation trails
or contrails, thus additionally influencing the local radiation balance
of the atmosphere.

[0007] Contrails often manifest themselves as white "linear clouds"
(linear cirrus clouds) behind high-flying airplanes. Depending on
environmental conditions, a contrail can exist for several hours and can
propagate in such a manner that it makes a transition to a (large-)
area-shaped cirrus cloud cover. Investigations have shown that the
environmental conditions required for contrail formation occur relatively
rarely so that in the overall consideration of air traffic, contrail
formation results only in approximately 15 percent of all kilometres
flown. The visual characteristics of a contrail or the cirrus clouds
directly forming therefrom depend on particle emissions of the engine, on
particle formation in the exhaust gas stream, and on the environmental
conditions. The radiation effect of contrails is highly variable, both in
time and in space. At night, contrails heat up the local atmosphere,
while during the day they can also have a cooling effect at least over a
dark background. The heating radiation effect of contrails can reach an
order of magnitude that is comparable to that of the CO2 emitted by
airplane engines. The climate-relevant radiation effect of contrails is
at present neither directly recorded nor influenced by means of operative
measures.

[0008] From patent specification DE 103 59 868 B3, a method and a device
are known by means of which a contrail forming behind an airplane can be
detected. To this effect, cameras arranged in the rear region of the
airplane, which cameras point against the direction of flight and are
sensitive in the visible and/or infrared spectrum, record image data. By
means of suitable evaluation of the recorded image data, it is possible
to determine whether contrails have formed behind the airplane. Thus on
board an airplane an actual statement can be made as to whether a
contrail has formed behind the airplane.

[0009] From the article by Mannstein, H., Spichtinger, P., Gierens, K., "A
Note on how to avoid contrail cirrus", ELSEVIER Ltd., Transportation
Research, Part D, (2005) 10, pp 421-426, it is further known that the
environmental conditions required to form contrails, in particular ice
supersaturation in the atmosphere, typically occur only in atmospheric
layers of little vertical extension, so that a change in the altitude of
only +/-2000 ft (610 m) of an airplane flying in such an atmospheric
layer reduces the probability of contrails occurring by 50%.

[0010] In the state of the art it is thus possible, on board an airplane,
to detect whether the airplane generates a contrail at any given time. If
a contrail is generated, the airplane can prevent contrail formation by a
corresponding change in its flight altitude. With methods known from the
state of the art it is, however, not possible to determine on board an
airplane climate-relevant effects of a contrail generated by the
airplane. In particular, it has hitherto not been possible to detect
whether the contrail generated at any given time behind an airplane has
an atmosphere-warming effect or an atmosphere-cooling effect.

[0011] It is the object of the present invention to state a device and a
method for determining and indicating, on board an airplane, any
climate-relevant effects of a contrail produced by the airplane. In this
document the term "contrail" is used in a wide sense. The term includes,
in particular, also the above-described (large-) area-shaped cirrus
clouds that directly result from the contrail.

[0012] The invention is stated in the characterising parts of the
independent claims. Advantageous improvements and designs form part of
the dependent claims. Further characteristics, application options and
advantages of the invention are stated in the following description.

[0013] The device according to the invention for determining and
indicating, on board an airplane, any climate-relevant effects of a
contrail produced by the airplane comprises: first sensor means for
determining radiation data of short-wave and long-wave atmospheric
radiation directed upwards in the earth atmosphere at the location of the
airplane; second sensor means for determining the air temperature and air
humidity at the location of the airplane; a means for determining the
actual zenith angle of the sun at the location of the airplane; an
evaluation means with which a radiative forcing value produced by the
contrail can be determined based on the determined radiation data, the
air temperature, the air humidity and the zenith angle; and an indication
means for indicating the radiative forcing value and/or variables derived
therefrom.

[0014] Suitable first and second sensor means are known from the state of
the art to the average person skilled in the art and can be selected
depending on airplane-specific requirements or regulatory requirements.
In this context, preferably high-resolution sensors are used that are
polled with as high a scanning rate as possible (for example 1-10 Hz).
The short-wave atmospheric radiation can be acquired with the use of
so-called pyranometers; it preferably comprises a range of the
electromagnetic spectrum with wavelengths <4,000 nm, in particular of
200-3,000 nm. The long-wave atmospheric radiation can be acquired with
so-called pyrgeometers; it preferably comprises a range of the
electromagnetic spectrum with wavelengths >4,000 nm, in particular of
4,000-45,000 nm. The air temperature and air humidity of the ambient air
around the airplane are preferably acquired with the use of sensors that
are arranged side by side with little distance between them. Calculation
of the actual zenith angle of the sun at the actual location of the
airplane preferably takes place based on the actual time and the actual
position. The means is thus preferably connectable to a navigation system
of the airplane that provides the actual time and the actual airplane
position.

[0015] The term "radiative forcing" was introduced by the
Intergovernmental Panel on Climate Change "IPCC" in order to describe,
within the framework of climate studies, any external disturbance to the
radiation balance of the climate system earth. Such a disturbance can
occur in the form of a change in the concentration of a substance (e.g.
greenhouse gases, aerosols) relevant to the radiation balance, in the
form of a change in solar irradiance, or in the form of a change in the
natural cloud formation as a result of contrails. Each disturbance of the
radiation balance has the potential to bring about changes in climate
parameters, and thus a new state of equilibrium of the climate system
earth. Radiative forcing is typically indicated in watts/m2.
Radiative forcing is negative in the case of a disturbance in the
radiation balance that has a cooling effect on the atmosphere. Radiative
forcing is positive in the case of a disturbance in the radiation balance
that has a heating effect on the atmosphere. At the time, the concept of
radiative forcing was related, by the IPCC, to disturbances in the global
radiation balance relative to pre-industrial radiation balance values. In
this document the term "radiative forcing" (radiative forcing value)
indicates a disturbance, produced by a contrail, of the local atmospheric
radiation balance at the location of the airplane.

[0016] For the purpose of determining a radiative forcing value caused by
a contrail based on data of short-wave and long-wave atmospheric
radiation directed upwards in the earth atmosphere, the air temperature,
the air humidity and the zenith angle of the sun, various calculation
methods, approximations and parameterisations are known from the state of
the art to the average person skilled in the art. Examples are the
articles by T. Corti and T. Peter, "A simple model for cloud radiative
forcing", in Atmos. Chem. Phys., 9 5751-5758, 2009; Schumann et al., "A
contrail cirrus prediction tool", Proc. Intern. Conf. on Transport,
Atmosphere and Climate-2 (Aachen and Maastricht) 2009; and presentation:
Schumann et al., "A Parametric radiative forcing model for cirrus and
contrail cirrus", ESA Atmospheric Science Conference, Barcelona, 7-11
Sep. 2009.

[0017] At the present state of knowledge, based on the input data
described above, at least a corresponding assessment of the radiative
forcing value caused by the contrail can be determined.

[0018] Preferably, the indicating means is arranged in the cockpit of the
airplane in the field of view of the pilot so that the pilot understands
whether a contrail generated behind the airplane actually has a cooling
or heating effect on the atmosphere, and also understands the extent of
this effect at any given time. For this purpose the indicating means
indicates the determined radiative forcing value and/or a variable or
information derived therefrom. The pilot can thus, for example, in a
targeted manner maintain the flight altitude if a contrail formed behind
the airplane has a cooling atmospheric effect. In the case of a heating
effect on the atmosphere the pilot can in a targeted manner change the
flight altitude until contrail formation no longer occurs. The device
according to the invention thus allows targeted influencing, by the
pilot, for example on the flight altitude, depending on a desired climate
effect, based on a contrail generated by the airplane.

[0019] In the present document the determined radiative forcing values
preferably relate to the flight distance of the airplane, and are, for
example, integrated over the average life of the contrail, and are stated
or indicated in the unit GJoule per km. On board the airplane it is thus
possible to determine a radiative forcing value for each flight kilometre
travelled. It is thus possible to acquire a time series of radiative
forcing values from takeoff through to landing of the airplane. This time
series then, along the flight path, indicates the disturbance to the
local atmospheric radiation balance as a result of contrail formation.

[0020] As mention above, contrail formation depends not only on the
ambient air temperature and humidity, but also on further parameters, for
example the particle concentration in the engine exhaust gas and in the
ambient air (compare for example: J. E. Penner et al. "Aviation and the
Global Atmosphere", chap. 3.2.4, "Contrail and Ice Particle Formation",
IPCC 1999, Cambridge University Press, or: F. Immler et al. "Cirrus,
contrails, and ice supersaturated regions in high pressure systems at
northern mid latitudes" Atmos. Chem. Phy., 8, 1689-1699, 2008). Since
these additional parameters actually are not acquired, errors can occur
in determining radiative forcing values, if according to an algorithm
stored in an evaluation means, based on the actually determined ambient
air temperature and humidity, contrail formation results, with this
contrail formation however not occurring in reality.

[0021] In order to minimise this error as far as possible, the device
according to the invention preferably comprises one or several cameras
that in the direction of flight point rearwards, and a corresponding
automatic image evaluation system for contrail recognition, as disclosed
in the above-mentioned patent specification DE 103 59 868 B3. In this
improvement of the device according to the invention the image evaluation
system is connected to the evaluation system. If the image evaluation
system detects contrail formation, this serves to verify the algorithms
for contrail formation, which algorithms have been stored in the
evaluation system. Preferably, in this case a radiative forcing value is
determined only if the image evaluation system has detected contrail
formation. Also imaginable in this context are self-learning algorithms
for contrail formation, which algorithms are stored in the evaluation
system and which continuously optimize themselves based on the actual
contrail formation verified by the image evaluation system.

[0022] Of course, other methods and devices for verification of actual
contrail formation are also useable, for example the use of laser
scanning of the region which in flight direction is situated behind the
airplane, and with corresponding evaluation of the backscattered signals.

[0023] A preferred improvement of the device according to the invention
comprises a first interface, by way of which prognostic weather
simulation data relating to the environment of the airplane can be
provided for the evaluation means. Furthermore, the evaluation means
comprises a first module, by means of which, based on the prognostic
weather simulation data, the radiation data, the air temperature, the air
humidity and the zenith angle a lifespan of the contrail can be
determined, as can the entire radiation effect of the contrail integrated
over its lifespan. Finally, in this improvement the radiative forcing
value is determined by the evaluation means based on the integrated
overall radiation effect of the contrail.

[0024] Based on the prognostic weather simulation data it is thus possible
for the first module to simulate for the future, or predict, the
development, in time and in space, of the contrail generated in the
atmosphere, dependent on actual weather events. The radiative forcing
values generated in this process thus take into account actual weather
developments and are thus more realistic or more accurate than radiative
forcing values that are determined based on approximations and without
any reference to actual weather events. The weather simulation data
required for this correspond, for example, to the data as provided by the
numerical weather forecasting model of the ECMWF (European Centre for
Medium-Range Weather Forecasts) or the German meteorological service
(Deutscher Wetterdienst). Calculation of the development in time and
space of the contrail based on weather simulation data is based on known
approaches which, for example, are used in corresponding trajectory
models.

[0025] The device according to the invention preferably comprises a
receiving unit for wirelessly receiving weather simulation data and for
providing the weather simulation data at the first interface. In this
manner it can be ensured that calculation of the development in time and
space of a contrail by the first module always takes place based on the
most up to date weather simulation data. In this context radio
transmission of corresponding weather simulation data, for example of the
ECMWF weather forecast model, is imaginable. As an alternative, the
device can comprise a computer unit on board the airplane, which computer
unit generates the prognostic weather simulation data and provides it at
the first interface. However, this computer unit requires meteorological
initialisation data that is as current as possible, which data is, for
example, provided shortly before commencement of the flight.

[0026] The lifespan of a contrail can, for example, be assessed from the
parameters of humidity, temperature and vertical speed, wherein it is
assumed that a contrail will distinguish itself from its surroundings
until such time as the so-called Koop-limit for homogeneous ice
nucleation has been reached.

[0027] The integrated overall radiation effect of the contrail and thus
the radiative forcing value is preferably determined in relation to a
flight distance, in other words the overall radiation effect or the
corresponding radiative forcing value is in each case determined over the
lifespan of a contrail sector, for example measuring 1 km in length. As
an alternative or in addition, for example by means of summation of the
overall radiation effects of the individual contrail sectors, a radiative
forcing value relating to the entire contrail generated behind the
airplane can be determined and indicated.

[0028] A further preferred embodiment of the device according to the
invention comprises a second interface, by way of which fuel consumption
data of the airplane can be made available to the evaluation means,
wherein the evaluation means comprises a second module, by means of which
based on the fuel consumption data a radiation effect of greenhouse gases
emitted by the airplane can be determined. In this improvement the
radiative forcing value determined by the evaluation means, apart from
being based on the radiation effect of the contrail, in addition is based
on the radiation effect of the emitted greenhouse gases. Radiative
forcing generated by the greenhouse gases is largely determined by the
fuel consumption alone. As explained above, the greenhouse gases, without
exception, generate positive radiative forcing, while contrails,
depending on environmental conditions, can generate positive or negative
radiative forcing. In this improvement both effects are taken into
account and are indicated separately or summed.

[0029] The device according to the invention preferably comprises a
storage unit for storing determined radiative forcing values and/or
variables derived therefrom. Furthermore, a transmitting unit for the
wireless transmission, to a receiving station, of the determined
radiative forcing values and/or variables derived therefrom can be
provided. Both of the above are used for possible subsequent evaluation
of the radiative forcing values acquired during the flight.

[0030] A second aspect of the invention relates to a method for
determining and indicating, on board an airplane, climate-relevant
effects of a contrail produced by the airplane.

[0031] The method according to the invention comprises the following
steps:

[0032] determining radiation data of short-wave and long-wave atmospheric
radiation directed upwards in the earth atmosphere at the location of the
airplane; determining the actual air temperature and the actual air
humidity at the location of the airplane; determining the actual zenith
angle of the sun at the location of the airplane;

[0033] determining a radiative forcing value, produced by the contrail,
based on the determined radiation data, the air temperature, the air
humidity and the zenith angle; and

[0035] For an explanation of the method according to the invention
reference is made to the above information provided in the context of the
device according to the invention, which information can analogously also
be transferred to the present method.

[0036] A first advantageous embodiment of the method is characterised in
that with the inclusion of provided prognostic weather simulation data
relating to the atmospheric environment of the airplane a first lifespan
of the contrail and an overall radiation effect of the contrail, which
radiation effect has been integrated over the first lifespan, are
determined, and the radiative forcing value is determined based on the
integrated overall radiation effect of the contrail.

[0037] A second advantageous embodiment of the method is characterised in
that with the inclusion of actual fuel consumption data of the airplane a
radiation effect of greenhouse gases emitted by the airplane is
determined, and the radiative forcing value is additionally determined
based on the radiation effect of the emitted greenhouse gases.

[0038] Preferably, prognostic weather simulation data can be wirelessly
transmitted from a ground station to the airplane where it can be made
available. As an alternative or in addition the weather simulation data
can be generated and provided on board the airplane. Particularly
preferably, the determined radiative forcing values and/or variables
derived therefrom are stored on board the airplane and/or are wirelessly
transmitted to a ground station.

[0039] With air traffic presently showing the highest growth rates of all
modes of traffic, its share in global warming will in the foreseeable
future continue to increase, as will the necessity to take measures for
reducing the effect of air traffic on the climate. The present invention
can contribute to reducing damaging climate-relevant effects of air
traffic in that already in flight from the combination of radiation
measuring, temperature measuring and humidity measuring the radiative
forcing expected locally as a result of contrails is evaluated and is
available, by way of a display in the cockpit, as a basis for making
decisions relating to any changes in flight altitude or in the route.
Furthermore, measures that have already been taken during flight
planning, i.e. prior to takeoff of the airplane, can be verified in
relation to their success.

[0040] In summary, from measuring the radiation flow density of short-wave
and long-wave atmospheric radiation directed upwards, from the ambient
temperature and the ambient humidity in conjunction with the solar
position determined by indications relating to position and to time, the
radiative forcing of a contrail as it is generated at cruising altitude
is assessed or determined. Parameterisation of the radiative forcing,
which parameterisation corresponds to this problem, as a function of the
visual thickness of a contrail, the temperature, the position of the sun
and the radiation flows directed upwards can be taken from the state of
the art. The determined radiative forcing value is indicated on a display
and is preferably stored for evaluation at a later stage. With the
inclusion of a weather forecast, which either prior to the flight
corresponding to flight planning provides the atmospheric state in the
vicinity of the flight route, or by a linkage to an online weather
information system, as conceived, for example, in the project "WxFUSION"
of the EU (European Community) EU-FLYSAFE, 2005, by estimating the future
development of the contrail, in particular of the expected lifespan of a
contrail, it is not only possible to determine the actual radiative
forcing, but also the radiation effect integrated over the lifespan of
the contrail. The integrated radiation effect, which can be assessed by
means of a trajectory model, preferably taking into account the radiation
effect of the emitted long-lasting greenhouse gases, which by way of the
fuel flow are acquired anyway in the airplane, determines the effect
which contrails and resulting cirrus clouds have on the climate.

[0041] The invention is of particular economic interest if in the context
of efforts to reduce climate change it is not only long-lasting
greenhouse gases, so-called "Kyoto gases", but also other anthropogenic
influences, for example contrails produced by airplanes, on the climate
are taken into account and are incorporated in regulatory measures, for
example in emission trading. In this case the present invention can
document the efforts relating to climate-effective measures.

[0042] Further advantages, characteristics and details are disclosed in
the following description which describes one exemplary embodiment.
Described and/or illustrated characteristics per se or in any sensible
combination form the subject of the invention, if applicable also
independently of the claims, and can, in particular, in addition also
form the subject of one or several separate application/s. Identical,
similar and/or functionally identical components have the same reference
characters.

[0043] The following are shown:

[0044]FIG. 1: a highly schematised representation of a device according
to the invention on board an airplane.

[0045]FIG. 1 shows a diagrammatic view of a device according to the
invention for determining and indicating, on board an airplane (101), any
climate-relevant effects of a contrail produced by the airplane (101),
comprising: first sensor means (102, 103) for determining radiation data
of short-wave and long-wave atmospheric radiation directed upwards in the
earth atmosphere at the location of the airplane (101); second sensor
means (104, 105) for determining the air temperature and air humidity at
the location of the airplane (101); a means (106) for determining the
actual zenith angle of the sun at the location of the airplane (101); an
evaluation means (107) with which a radiative forcing value produced by
the contrail can be determined based on the determined radiation data,
the air temperature, the air humidity and the position of the sun; and an
indication means (108) for indicating the radiative forcing value and/or
variables derived therefrom.